Analysis: Processor mimics ear, gets 25 dB SNR gain

Figure 2. Simplified system architecture.

The signal path taken by the input from two microphones is illustrated by Figure 3, which shows a different view of the processing:

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Figure 3. A1010 Signal processing system diagram.

The chip design pays careful attention to power consumption in every mode. Key to the processing power is a custom DSP with special instructions which accelerate the FCT and other key operations. The on-board RAM and ROM are apparently sufficient to handle all necessary operations.

The live demo at the Hot Chips presentation by Watts showed impressive capabilities of the technology's capabilities in a noisy environment, while showing the parameters in the analysis. The displays resemble the familiar "Waterfall" displays used in speech processing and elsewhere (Figure 4).

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Figure 4. Spectral Representation using the Fast Cochlea Transform.

The company claims an average improvement of 0.77 in Mean Opinion Score (MOS) measure of audio quality in phone applications. (On a scale of 5, 4.3 represents toll-quality speech). With such an improvement, phone systems with marginal performance can reach acceptable quality levels.

Other approaches to the noise problem in the mobile environment have included Noise Cancellation Technology such as Aurisound's Adaptive Focus-Beam (AFB) technology on CSR's BlueCore5-Multimedia platform. Audience's technology goes beyond noise cancellation by understanding the way humans actually hear.

The Audience technology resulted from years of work by founder Lloyd Watts and others at Caltech, Interval Research and other institutions. Audience' Advisory board includes several luminaries that practitioners of DSP will recognize such as Larry Rabiner and Carver Mead. Their technology and implementation in the A1010 processor bode well for future applications. (Audience already announced design wins in high-end phones from Sharp and LG, with more in the works.)

In fact, I have a product idea for Audience; how about a hands-free (Bluetooth) headset for cyclists? I often see cyclists talking on the phone, thereby leaving just the other to control their steed. It seems odd that the very people who are adopting a healthy and environmentally correct lifestyle would endanger their own lives. Current solutions seem to consist mainly of a holder for the phone that attaches to the handlebar with a conventional Bluetooth headset.

About the author
Shiv Balakrishnan has more than 25 years of experience in signal processing including 12 years at Tektronix. He has held engineering and technical marketing positions in startups as well as Fortune 500 companies like Philips, Sun and TI. His consulting work spans the range from signal processing system design to market research and competitive analysis. Shiv is named co-inventor on multiple DSP and wireless patents. His undergraduate degree is from the Indian Institute of Technology and graduate studies were at the University of Florida and Purdue University.